1. Field of the Invention
The present invention relates to a vector detecting device that detects a vector of an AC signal with known frequency. More particularly, the present invention relates to a living-body complex impedance measuring apparatus that measures living-body impedance by detecting a vector of a signal from a living body in which an AC signal having a known frequency flows.
2. Description of the Related Art
Conventionally, in a vector detecting device that detects a vector of an output as a target, and an impedance measuring apparatus that measures impedance of which a vector is detected, a phase detector detects a vector of an, output from a measuring target, an integrator smoothes and integrates the output of which the vector is detected, and an A/D converter converts an analog output which is smoothed and integrated into a digital signal (see, e.g., Japanese Unexamined Patent Application Publication No. 4-80667 (Patent Document 1) and Japanese Unexamined Patent Application Publication No. 4-109174 (Patent Document 2)).
However, in the above-described conventional apparatus, the integrator integrates the output only to amplify the detected vector from the phase detector. Therefore, in the conventional apparatus, an offset voltage of the integrator is generated and, disadvantageously, an expensive A/D converter is needed independent of the integrator.